bugfix: data race in head.Appender.AppendHistogram and Commit#15142
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krajorama merged 2 commits intoprometheus:mainfrom Oct 14, 2024
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bugfix: data race in head.Appender.AppendHistogram and Commit#15142krajorama merged 2 commits intoprometheus:mainfrom
krajorama merged 2 commits intoprometheus:mainfrom
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Two Appenders race when creating a series with a native histogram as the memSeries will be common and the lastHistogram field is written without lock. Signed-off-by: György Krajcsovits <[email protected]>
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Move writing memSeries lastHistogramValue and lastFloatHistogramValue after series creation under lock. The resulting code isn't totally correct in the sense that we're setting these values before Commit() , so they might be overwritten/rolled back later. Also Append of stale sample checks the values without lock, so there's still a potential race. The correct solution would be to set these only in Commit() which we actually do, but then Commit() would also need to process samples in order and not floats first, then histograms, then float histograms - which leads to not knowing what stale marker to write for histograms. Signed-off-by: György Krajcsovits <[email protected]>
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beorn7
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Thanks for making things less bad… Looking forward to the Commit reorganization. (I have only vague memory why we did the floats first thing. It was probably much easier that way, and we didn't think about staleness back then.)
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Benz1993com
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jesusvazquez
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Leaving it open for you to merge 👍 |
fionaliao
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Tusenka
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This was referenced Oct 14, 2024
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Created issue #15177 to track the refactor. |
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Fixes: #15139
Two Appenders race when creating a series with a native histogram as the memSeries will be common and the lastHistogram field is written without lock.
Fix by:
Move writing
memSerieslastHistogramValueandlastFloatHistogramValueafter series creation under lock.
The resulting code isn't totally correct in the sense that we're setting
these values before
Commit(), so they might be overwritten/rolled backlater.
Also
Append()of stale sample checks the values without lock, so there'sstill a potential race.
The correct solution would be to set these only in
Commit()which weactually do, but then
Commit()would also need to process samples inorder and not floats first, then histograms, then float histograms - which
leads to not knowing what stale marker to write for histograms.
Might be easier to do after : #15112